Antiblurring device for aerial cameras



ay 9, H95@ o. SANDVEK ETAL ANTIBLURRING DEVICE FOR AERIAL. CAMERAS Filed Nov. 27, 1945 Patented May 9, 1950 AN TIBLURRING DEVICE FOR AERIAL CAMERAS Otto Sandvik and Jasper S. Chandler, Rochester, N. Y., assignors, by mesne assignments, to the United States of America as represented by the Secretary of War Application November 27, 1945, Serial N0. 631,004

7 Claims.

This invention relates to aerial cameras and more particularly to a device for oscillating an aerial camera in order to compensate for the speed and altitude of an associated aircraft from which pictures of the terrain are being taken.

The blurring effect produced by movement of the plane relative to the ground may be effectively eliminated if the camera is rotated in such a way as to cause the optical axis to pass through a xed point on the ground during exposure. It has been found that the change of angular position and distance of ground objects relative to the camera are of secondary importance for the usual exposure, lm speed and altitude. The method of providing pivotal motion of a camera at a certain rate may be termed a sweep method and the mechanism disclosed herein will be hereinafter referred to as a sweep mechanism. There appear to be certain advantages of the sweep method over other methods which may require optical complications and accurate moving mechanisms and have the attendant risk of deterioration of the optical denition.

Accordingly, it is an object of our invention to provide a sweep mechanism of a relatively simple nature for pivoting a camera at a predetermined rate during exposure in order to compensate for the ground speed and altitude of an associated plane to eliminate blurring of the photographic image.

A further object of our invention is to provide a structure having combined sweep and intervalometer functions in the same device and utilizing common elements to a large extent, thereby eliminating the need for extra equipment and providing an economical and compact unit for use in conjunction with aerial cameras.

Figure 1 is a graph of the Time vs. Altitude cycle for a series of velocities of an aircraft having a camera mounted thereon with a twentyfour inch focal length lens and a 9" film width and incorporating our invention.

Figure 2 is a schematic illustration partially in perspective, illustrating the mechanical and electrical elements of our device, parts being broken away and shown in section; and

Figure 3 is a perspective view illustrating the general camera supporting arrangement in a boxed unit housing the elements illustrated in Figure 2.

where:

T=Time interval between successive pictures, in

seconds;

w=Picture width in the direction of flight, in

inches;

A=Altitude of plane in feet;

"=Focal length of lens, in inches;

V=Ground velocity in miles per hour;

It may be further shown that FlAsH-v (2) Where:

v=Required compensatory velocity of image travel to hold image xed with respect to the lm during exposure, in inches per second;

By combining these two equations it will be found that from whence it will be seen that for a iixed value of w, v is dependent only upon the interval T and from which it follows that the sweep mechanism may be automatically set for a required o when the intervalometer sub-combination of our invention is properly set, all as will be hereinafter described in detail.

The sweep mechanism may impart any suitable movement to the camera as long as the proper Velocity is imparted during exposure and the camera returned to the initial position so that the cycle may be repeated at an interval of T seconds. The duration of exposure is extremely short compared to the interval T so that a sinusoidal movement is entirely adequate if exposure takes place at the midposition of the backward sweep of the camera as it oscillates about an axis transverse to the Hight path.

By way of further explanation, attention is 3 called to Figure 1 of the drawings which shows a graph of T Vs. Altitude for a series of 'velocities of an aircraft. This graph is for a camera havu ing a twenty-four inch focal length lens and film width of nine inches in the direction oi' night, which is conventional for military and it will be understood that the graph rcpresents time intervals for the usual sixty percent overlap. For the camera described, equation one and the graph shows the upper and lower limi-ts of altitude at a given velocity, it 4being understood that the time interval 'in seconds is ladjusted within the range of from six to twenty seconds in this case, depending on 4the speeiii'c velocity and altitude to flin-rinato blurring of photographs. Y'

The details of our invention will now be described in conjunction with tliieiotl-rer figures the drawings; namely, Fig. 2 which shows schematically, and partially in perspective, the electrical and mechanical eiements of our device; and

Fig. 3 which iis al perspeetives'howing the general larrangements f'o-'f anfaerial camera and a boxed Vunit housing ytheelements illustra'tetl--in Fig. 2.

Wifthfreierence to Figs. Ziand the components of :our inventioncomprise 'a Vring mount A fon r which the camera'isfs'ecured. `v'Ih'e ring mount A is broadly defined as a camera element for our purposes and comprises a ring 3, pivotally supported for movement about an axis :cwithin an outer ring l iiXed to the aircraft fuselage, and .la ring f5 abovean'd securedr to y:ri-ng 13 through cushion devices 1, it being understood'ithat 'the fcamera is rigidly fsecured to fthe rng 5 ibyzclamps A and that it pivots with the rings 3 and about the axis -:r whichextends transversely .of the path of night. AimotorB-supplies 'mechanical driving power for oscillating-themingmount in and a mechanismC is..provided.through .which the ring mount is driven. An electrical circuit .D is used in conjunction with the mechanism C for energizing the motor predetermined by a manually operable speed control arrangement The various elements ofv our invention B through E are adapted'to be housed-'in -Ia casing for convenient "mounting in Iconjunctionwith 'ring y mount as iilustreitedin Fig; 3.

Attention :is :nowfcalled to .iFigsZ wherein is zdisclosed a manually operable knob l securedrtoa shaft i2 which has a threaded portion it inter- Kmediate its length anlterminates in a potentiometer comprising a rotary arm IB which engages are'si's'ta-nce wire winding f8. The potentiometer -elemen'ts 4liffand f F8 are c'onr-iected to the motor energizing circuit iinsuc'h a manner that rotation of shaft `I' 2 'increases -orfdecr'eases Vtheiresistance 'inV series with ithe armature andl 'held Yof :the motor iB, kdependinglon Ithe fdireotionfof :rotation of knob IB for the purpose of providing'a predetermined vfsp'eedof Amotor-B ini-accordance with YKa-selected 'time interval betvfeenjpictu-re's as indicated by' a "calibrated `scale '|9. #The ithre'aded 'portion 'ilf :engages ja nut member l2l] which is `guided for reciprocal motionY by fai bar-i122, 'member 25' lbeing arranged to slide on bar `212. Member 2t has -a pair of integrally Asecured rods V244 iarranged ina forked `coniiguration 'and adapted to engage the A'forked arms ofam'e-m'ber 42S 'which iis pivotally Ysecured atthe'iixed point f28's'o asltofberockable about the pivot prqvid'edatZB when'the-knob 'it is turned, causing *tneenut meinbertu to-ride Yup "tical, at a, b 'and' c, it being unders'toOdthatthecontact Apoints at c are noimally'engaged while those'at'b or down on shaft I2. As will be seen on the drawing, member 26 has an additional pair of forked arms 27 which carry buttons 32 of any suitable frictional material. The buttons 32 are adapted to frictionally engaged a plate 34 which is slidably arranged on a shaft 35 of the motor B, being reciprocated thereon by a conventional flyball governor 38, which may be of the spring loaded type fixed to shaft 36 at 4D. 'Ihe arrangement is such that the irictional buttons 32 are Vbrought closer to the .plate 3d by'afdjustment of 'knob iffor proportionately lower speeds of the motor B so that should any tendency for the `motor to overspeed develop, plate 35i will be brought into irictional engagement with buttons .-32 to counteract the tendency. The motor B drives the mechanism C which comprises a worm `gear fl' driving-'a worm wheel t5 which through a pinion drives-a gear 5D, whence rotation is transmitted'thro'ugh a shaft 52 to an eccentric member 5 adapted to actuate a strap and rod .erfiber, causing-oscillation of a link 53 about anxed ,pivot point ti). Link 58 has at one end thereoiF a nut member t2 which threadedly engages a threaded portion 64 of anadjustable levsling member 'eE'having'an'etremity se pivotally secured to the'ring mount A bymeanstoi a 'ball joint, "as shown, and having itsY other extremity Vprovided lwith 'afknob Til for `convenient ad'- jus'tment :to level the 'ring mount A. "The gear "5@ has an 'interrupter'zrn'ember "f2 f'se'cured thereto which' 'is adapted Yto engagery 'and d'e'ii'ect alexibl'e 'spring leaf it at -a,prede'termined point in 'the travel ofnen'ber *12, it l'beingi particularly noted -that 'such predetermined tpoint A"Correspends'to the point-'at which ring'mount A is in -a horizontal posit-ion, with Vthe loptical faX'i's 'of the'camera ver- Spring leaf *it actuatesfpairs of contacts and 'care normally disengaged. Power vis sup- A plied from the line JVdirectlyto the 'contact 'points at 'a and thence to a double-'pole bdouble-'throw lswitch ""S `and 'it will "benoted that whenthe swtohis' in th'evon p'ositionciirrefn't flows to'the switch point "Si thencethrougth Lthe `Contact poi-'nts at ato the "armature "biftthat there is-'a simultaneous path :provided "s'othat current; also ows 'through theswitchfrom'Si directlyto'the armar ture, i. e., whenthe Switch is the0n position current 'goes VVAto "the armature "independently or any current path 'through thec'ontac't points at a. Accordingly, itwillbe seen that-disengagement of Athecontacts'at a'by denectionoflileafll as effected by the revolving interrupter memben'would 'hai/eno effectonthemotor provided theswitch S "The electrical circuitvarrangement 'is 'suchthat 'the 'motor B `then rotates a't very reduced speed. depending `onthe Avalues "oi the resistances :te and ft2 so thatwhen the interruptor member fznext "del'ects thelea'f it, thusibreaking"thecontactat a, there 'Willbe littl'eor no inertiain'the motor 1or 4in the mechanical parts of the system tending s, to cause any appreciable over-travel of the ring .mount A past the point at which it was in its oscillatory path at the instant engagement of the contacts at a was broken. It is contemplated as heretofore explained that the ring mount A will be level or horizontal at the vtime of disengagement at a so that the camera will be in normal vertical position, that is the optical axis thereof will be erected for normal picture taking use.

It will be noted that our device trips the shutter at the instant that the optical axis of the camera is in verical position, the mechanical arrangement being such that the camera is in a backward sweep with reference to the direction of flight during exposure, although obviously the instant of tripping with respect to the inclination of the camera could be adjusted as desired by means of the knob IEB.

We believe that our teaching may be used for motivating other camera elements besides ring mounts, e, g., lenses or film magazines, to achieve an anti-blurring effect, and we seek protection for our invention within the scope of the following claims.

We claim:

l. In aerial camera supporting apparatus of the class described for use in conjunction with an aerial camera and shutter for taking photographs of the terrain below from an aircraft while flying thereover, a support to be xedly carried by the aircraft, a camera support tiltabl; carried by the fixed support for oscillation about a horizontal axis transverse to the direction of travel of the aircraft, a motor carried by the xed support including a motor drive circuit, oscillating means including actuating connecting means between the motor and the camera support at one side of the oscillation axis for oscillating the camera support in the vertical plane of travel of the aircraft to prevent relative movement of the photographic axis of the camera at the intersection of said axis with the terrain being photographed during oscillating movement of the camera support in one direction, means operable by said oscillating means for actuating the camera shutter at a predetermined point in the swinging movement of the camera support in said one direction, means for varying the length of the actuating connecting means to adjust the relative position of the arc of oscillation of the camera support to vary the position in the said arc where the camera shutter is actuated, to adjust the position of the camera photographic axis, relative to the plane of the terrain being photographed at the time when the camera shutter is actuated to make the photographic exposure.

2. Apparatus as claimed in claim 1 including an electric motor drive circuit connected to the motor for operating the same at a predetermined speed, and variable resistance means in said motor drive circuit for varying the speed of the motor to compensate for change in the speed of the aircraft while traveling across the terrain being photographed.

3. Apparatus as claimed in claim 2 including switch and secondary motor circuit means in said motor drive circuit for introducing a secondary control circuit and resistance in the motor drive circuit for operating the motor at a reduced speed, interrupter means in said secondary control circuit for interrupting the secondary control circuit to stop the motor, including means operable by the actuating connecting means, for interrupting the motor circuit at a predetermined position in the oscillation of the camera support.

4. In a mechanism of the class described for use in conjunction with an aerial camera, a motor means, an operating circuit therefor, manually operable speed control means in said operating circuit for regulating the speed of said motol` means, a camera support tiltable about a horilrental axis transverse to the direction of travel of the aerial camera when carried by an aircraft over a terrain to be photographed, actuating means between the camera support and the motor for swinging the camera support about its tilt axis to maintain a photographic image of the terrain below an aerial camera that is carried by said camera support, substantially stationary on the camera focal plane during travel over the terrain, an interrupter member, a motor control circuit controlled thereby, means operable by said actuating means for actuating said interrupter member to open said motor control circuit at a predetermined point in the swing of said camera support and switch means for connecting said motor control circuit in said motor operating circuit ior arresting tilting movement of the camera support at said predetermined point in its oscillation.

5. In a mechanism of the class described for use in conjunction with an aerial camera, a motor means, manually operable speed control means for said motor means, means driven by said motor means for actuatinga camera element to maintain aphotographic image in iixed position on the focal plane oi a camera, an interrupter member associated with said latter means and actuatable responsive to motion thereof, and an electrical circuit associated with said interrupter member and adapted to deenergize said motor responsive to actuation by said interrupter member at a predetermined point in the travel of said latter means, wherein said motor means comprises an electric motor and wherein speed control means comprises a variable resistance in said motor circuit, said electric circuit comprising a pair of normally engaged contact points adapted to be disengaged by said interrupter member, manually operable switch means in said motor circuit and connected in parallel with said normally engaged contact points to said motor, fixed resistance means connected to said manually operable switch means and adapted to be placed in said motor circuit in substitution for said variable resistance means when said manually operable switch means is in cut-oit position, whereby rotation of said motor continues subsequent to operation of said switch means to cut-off position unt-il said contact points are disengaged by operation of said interrupter member at a predetermined point in the travel of said camera element.

6. In a device as set forth in claim 5 including a pair of normally disengaged contact points adapted for engagement by operation of said interrupter member substantially contemporaneously with disengagement of said normally engaged contact points.

7. In a mechanism of the class described for use in conjunction with an aerial camera, an electric motor, manually variable speed control means for said motor comprising a potentiometer connected in said motor circuit in such a manner as to maintain substantially constant armature and field current, mechanical means driven by said electric motor for actuating a camera element to maintain a photographic image in substantially xed position on the focal plane of a camera, an interrupter member driven by said mechanical means, an electric circuit associated with said .motor ,and'comprising a pair of no1'- mally engaged vcentactpoints adapted to berdisengaged by'sd interrupter mem-ber at a prei determined point inthe -tr'avel thereof, al vdcmblepole, dlibIe-throw manualiyyoperable swtcnan'd 5 a; visita/ge divider resistancel in said'electric circuit, saidv switchandsdidllatter resisted-1eek and ysaid po tenti'ometer being so connectedas to place said` re- Y sstancein the armaturerand eldfrcircuts of said motor in substitutionfor saidp'osentiometer when Saidfsivitch is incut-,oigpositiom wherebyoperation lof seid` motor cnntinues untilsadinterrupter member reachesrsaid :predetermined point in Vits traveL thereby vcamsiifig :disengagement -of said 8 REFERENGESI CITED The foilowing re-:erenclfas are of record in the `file of thispatent:

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